I have a 1420 with standard rotor. Green stem soybeans have really been a problem the last couple years. I have a 15' 820 header and can only combine at 2 to 2.5 mph. Is there anything that I can change or modify to speed up a little. I have large wire concaves and keystock grates. I have heard about others taking out straight rasp bars. Any help would be greatly appreciated.